Quote Originally Posted by TeutonicKnight
I usually have to click on the land on the other side of the bridge, and hit the backspace key to stop them when they get far enough along to be where I want them to be.
This the method I use. Even if I am the attacking party this is usually sufficiant to provoke the defenders into rushing you on the bridge. This sets up a decent "defending" situation even if you are attacking. grind the enemy away and when they rout, charge across!